1. Field of the Invention
This invention generally relates to a bicycle power sensing apparatus. More specifically, the present invention relates to a bicycle power sensing apparatus that measures a force acting on a part of a bicycle for indicating a pedaling power of a rider.
2. Background Information
Recently, some bicycles are provided with cycle computers for providing information (e.g., operating conditions, rider performance, etc.) to the rider. Also some bicycles are provided with electronic bicycle components for assisting the rider in operating the bicycle or for adjusting an operating condition of the bicycle to improve the comfort or performance of the bicycle. Information on various operating conditions and rider performance are often used by electronic bicycle components that are adjusted based on the bicycle operating conditions. One particularly useful piece of information is the power exerted by the rider on the bicycle components due to the pedaling force applied by the rider.
One example of a bicycle power sensing apparatus is disclosed in the U.S. Pat. No. 7,861,599. In this patent, the bicycle power sensing apparatus measures a power exerted to rotate a bicycle wheel, a crank, or other rotating part. The bicycle power sensing apparatus is basically provided with a cadence sensor, a strain gauge, an amplifier, an A/D converter, a processor and a wireless transmitter. The cadence sensor measures cadence (the rotational speed of the crank). The strain gauge measures a strain of the crank shaft occurring when a rider is pedaling. The amplifier amplifies an analog electric signal outputted from the strain gauge to a range that can be processed by the A/D converter. The A/D converter circuit converts the amplified analog electric signal to a digital signal. The processor calculates a torque acting on the crank shaft based on this digital electric signal. The processor calculates a power imparted by the rider based on this torque and the cadence outputted from the cadence sensor. The wireless transmitter transmits the power or torque calculated by the processor to a cycling computer.